150 Years of Ozone Research: Challenges for Tomorrow

1. 150 Years of Ozone Research: Challenges for Tomorrow adopted from Guy P. Brasseur Max Planck Institute for Meteorology Hamburg, Germany

2. The First Steps in Greece • Greek philosophers including Empedocles (5th century BC) believed that nature is composed of earth, water, fire and air. • Aristotle (384-322 BC) realized that water was continuously recycled between the atmosphere and the ocean.

3. The First Steps Schoenbein

4. Fire-Air and Foul-air Joseph Black • Leonardo da Vinci (1452-1519) in Italy and John Mayow (1641-1679) in Great Britain discovered that air is composed of “fire-air” that supports combustion and life, and “foul-air” that does not. • Carbon dioxide is discovered around 1750 by Joseph Black (1728-1799). • Nitrogen is identified several years later by Daniel Rutherford (1749-1819).

5. Oxygen “Fire-Air” was isolated in 1773 by Swedish chemist Carl Wilhelm Scheele (1742-1786), in 1774 by British scientist Joseph Priestley (1733-1804) and by French chemist Antoine-Laurent Lavoisier (1743-1794).

6. Oxygen Lavoisier named this gas “oxygen” after the Greek o (oxus: acid) and  (geinomai: to generate). He was guillotined during the French Revolution, while Priestley, who was supporting the French Revolution, was on his to exile in America.

7. Noble Gases • John William Strutt known as Lord Rayleigh (1842-1919) and Sir William Ramsay (1852-1919) identified argon and other noble gases in the atmosphere. This discovery gave Ramsey the Nobel Prize for Chemistry in 1904. William Ramsay

8. The Discovery of Ozone • Dutch experimentalist Martinus van Marum (1750-1837) notes that the spark produced by a giant double plate-glass frictional electrostatic generator produced"the odor of electrical matter."He does not identify the gas generated by the spark, but notes that it tarnishes mercury.

9. The Discovery of Ozone • The gas discovered by van Marum remains un-named for 55 years, until in 1840, Christian Fredrich Schönbein(1799-1868) detects the same peculiar odor in the oxygen liberated during the electrolysis of acidulated water. • Schönbein names this gas “ozone” after the Greek word όζειν (ozein, to smell). In a letter sent in 1840 to Francois Arago and submitted to the French Academy of Sciences, Schönbein suggests that ozone could belong to the chemical group of chlorine or bromine.

10. In 1857 Werner Von Siemens designsan ozone generator

11. The Ozone Chemical Formula • In 1845, Auguste de la Rive and Jean-Charles de Marignac(Geneva) suggest ozone is a form of oxygen. • W. Olding (England), in his manual of chemistry(1861), suggests that the formula of ozone is O3 • In 1868 Jean Louis Soret(Basel) determine the density of ozone gas using Graham`s law of diffusion. He establishes quantitatively that ozone is an allotropic form of oxygen: OOO or O3 (oxygen dioxide).

12. The First Atmospheric Observations

13. The First Atmospheric Observations of Ozone • In 1858 André Houzeau(Rouen, France) develops a quantitative method (involving a mixture of iodine and arsenic) to measure ozone, and discovers that ozone is present in natural air. • French Chemist Albert Levy uses this chemical method to observe the abundance of ozone almost continuously from 1877 to 1907 at the municipal Observatory of Parc Montsouris in Paris.

14. The Optical Properties of Ozone

15. The Optical Properties of Ozone • In 1879, Marie Alfred Cornuobserves a sharp cutoff (300 nm) in the ultraviolet (UV) solar spectrum. • In 1881, Walter Noel Hartleymeasures the ozone absorption cross section in the laboratory and recognizes that this UV cutoff is produced by the presence of ozone in the atmosphere. • In 1913, John William Strutt (Lord Rayleigh) shows that the UV absorption does not happen in lower atmosphere Alfred Cornu Professor at Ecole Polytechnique in Paris

16. The Optical Properties of Ozone • In 1890, William Huggins reported several absorption bands in the observed spectrum of star Sirius between 320 and 360 nm. • In 1917, these bands were atributed by A. Fowler and R. J. Strutt to the presence of ozone in the atmosphere. • In 1920 at Marseilles, France, Charles Fabry and Henri Buisson used UV absorption properties to deduce that the thickness of atmospheric ozone was of the order of 3 mm STP W. Huggins

17. G.M.B. Dobson • In the 1920’s the British scientist, G.M.B. Dobson (Oxford University) developed a spectrophotometer that for many years remained the only accurate method to measure the ozone column abundance. • This instrument was installed at different locations, which led Dobson to estimate the latitudinal and seasonal evolution of the ozone column. • Dobson also discovered a strong influence of atmospheric dynamics on ozone.

18. The Dobson Ozone Spectrophotometer

19. Ozone Observations • Paul Götz during a Spitzbergen expedition in 1929 (by inverting Dobson spectrophotometer measurements at high solar zenith angles) shows that the maximum ozone concentration is located near 25 km altitude. • Götz and Hans Dütsch conducted systematic ozone observation in Arosa, Switzerland since 1926.

21. The Ozone Conferences

22. The First Ozone Conference in Paris (1929) • The first ozone conference takes place in Paris in 1929, and is co-chaired by Dobson and Fabry. • Sydney Chapman presents the first photochemical theory of ozone, and suggests that the formation of ozone results from the photolysis of molecular oxygen. • On the basis of the photochemical parameters available at that time, he suggests that the ozone layer is located near 45 km altitude.

23. The Second Ozone Conference (Oxford, 1936)

24. The Photochemical Theories

25. Ozone and Hydrogen • Sir David Bates (Belfast) and Baron Marcel Nicolet (Brussels), working together at Caltech in Pasadena, suggest that hydrogen radicals (H, OH, HO2) produced by photolysis of water vapor and methane provide a major ozone destruction mechanism in the mesosphere. • J. Hampson in Canada suggests that similar processes can destroy ozone in the stratosphere.

26. Ozone and Nitrogen • Paul Crutzen shows that the major ozone loss in the stratosphere is provided by a catalytic cycle involving the presence of nitric oxide (NO) • Nitric oxide is produced in the stratosphere by oxidation of nitrous oxide (N2O)

27. The Impact of Aviation • In 1971, Harold Johnston (University of California at Berkeley) suggests that the nitrogen oxides to be released by a projected fleet of supersonic aircraft could produce substantial ozone depletion. • An intensive research program, the Climatic Impact Assessment Program (CIAP) is sponsored by the US Department of Transportation (1972-1974).

28. Ozone and Chlorine • At a scientific conference in Kyoto, Japan in 1974, Richard Stolarski and Ralph Cicerone, then at the University of Michigan, suggested that chlorine could also catalytically destroy ozone in the stratosphere. • They note that large amounts of chlorine are released during volcanic eruptions

29. Chlorofluorocarbons and Ozone • In 1974, Mario Molina and Sherry Rowland at the University of California, Irvine, show that industrially manufactured chloro-fluorocarbons could provide the major source of stratospheric chlorine and therefore are a major threat to the ozone layer.

30. The Ozone Hole

31. The Ozone Hole: A challenge for the scientific community Observations made at the British Antarctic station of Halley Bay (Farman and coworkers) and the Japanese station Syowa (Chubachi) during the 1970’s and 1980’s show a dramatic decrease in the ozone column that is not simulated by atmospheric models. Halley Station

32. The Explanations • Early theories to explain the observed ozone hole refer to dynamical perturbations and solar variability. • Susan Solomon and colleagues suggest that chlorine can be activated on the surface of polar stratospheric cloud (PSC) particles observed over Antarctica, and can destroy most of the lower stratospheric polar ozone in a few weeks. • Considerable experimental work is initiated to study heterogeneous chemical processes

33. The Antarctic Ozone Hole • The most efficient catalytic reaction cycle responsible for the ozone hole is discovered by Mario Molina. • Airborne field campaigns and space observations confirm that anthropogenic chlorine is responsible for the formation of the ozone hole. • Substantial ozone destruction is also observed in the Arctic.

34. A Success Story The international protocol signed in Montreal, Canada in 1987, and the subsequent amendments, lead to a phase-out of the most ozone-damaging chlorofluorocarbons. The ozone hole is predicted to disappear around year 2050.

35. Paul Crutzen, Mario Molina, and Sherry Rowland receive the 1995 Nobel Prize in Chemistry for their seminal discoveries concerning the chemistry of ozone

36. This presentation is dedicated to Professor Hans Dütsch and Professor James R. Holton who passed away recently. Hans Dütsch Jim Holton